The present invention relates generally to a rotary angle sensing system, and more particularly to a sensing system that senses an angular position of a rotating shaft that reduces mechanical error, is economical to manufacture, and which can be extended to accommodate multiple rotation measurements.
One known example angular sensing system includes a non-contacting sensor element and an intervening mechanism between a shaft of interest and the non-contacting sensor element. An angular position of a rotating shaft is indirectly measured. A rotating shaft includes a gear that turns at least one additional shaft, the angular position of which is directly measured by the non-contacting sensor. The angular position of the rotating shaft is subsequently calculated based upon the direct measurement and the relationship between the measured shaft and the rotating shaft. Mechanical error, such as gear backlash, inherent in the addition of the intervening mechanism, appears in the indirect measurement of the angular position of the rotating shaft.
Another known example angular sensing system eliminates the intervening mechanism. This example system incorporates a pair of magnets to measure the angular position of the rotating shaft, whereas other angular sensing systems require only one magnet. As such, this example system is more expensive and complex to manufacture.
Further, known systems can only measure a relative angular position of a rotating shaft up to 360°. Known systems are unable to take into account that the rotating shaft may have completed, for example, two full 360° rotations prior to reaching its current angular position of 60°, and, as such, would have an actual angular position of 780°, i.e. [(2 revolutions)(360°)]+60°=780°.
Accordingly, there is a need for rotary angle sensing system that reduces mechanical error, is economical to manufacture and which provides multiple rotation measurement.